The Sol Computer was developed by Bob Marsh, Lee Felsenstein and Gordon French. Bob founded his company, Processor Technology, in April 1975 making 4K RAM memory boards for the Altair (cause MITS couldn't make a working memory board)

In June 1975, Bob and Les Solomon (technical editor of Popular Electronics) dreamed up the Sol-20 computer, Bob had a bunch of cheap walnut that he originally intented to use in a digital clock, he didn't want it to go to waste and used it in the Sol-20 (see picture).

About 10,000 of them were produced, some as kits, some as pre-builts. Based on the Intel 8080 microprocessor, this machine occupies a special niche in computer history for technical and esthetic reasons. It was one of the earliest to include a keyboard interface and support circuitry for full implementation of every 8080 function. It was a pioneer towards modern video output boards by having a design that actually put up alphanumeric characters on the screen, using a form of distributed processing that didn't lean on the CPU for all processing.

There were several models of the SOL-20 system :

- The SOL System I ($1649 in kit or $2129 assembled), with SOL Operating System, 8 KB RAM, a 12" TV/Monitor, and a cassette recorder with BASIC software tape.

- The SOL System II ($1883 in kit or $2283 assembled), is a SOL System I with 16 KB.

- The SOL System III ($4750 in kit or $5450 assembled), is a system II with 32 KB RAM, a video monitor, the HELIOS II Disk Memory System and a DISK BASIC floppy.